The present invention concerns a device for removing pollution from the exhaust gases of an internal combustion engine, of the type including an exhaust box containing, in series, a catalytic purification unit and a particle filter.
Such devices are used to remove pollution from automobile vehicle diesel engines in particular. The catalytic purification unit is adapted to treat pollutant emissions in the gas phase and the particle filter is adapted to retain particles of soot emitted by the engine.
The particle filter operates in accordance with a succession of filtration and regeneration phases. During filtration phases particles of soot emitted by the engine are deposited on the upstream face of the filter. During the regeneration phase the particles of soot, consisting essentially of carbon, are burned on the upstream face of the filter, in order to restore the latter""s original properties.
To favor the regeneration of the particle filter it is necessary to incorporate in the fuel feeding the engine a chemical agent which reduces the combustion temperature of the soot. The chemical agent is a catalytic additive containing one or more metallic constituents in the form of organometallic compounds. These burn in the combustion chamber of the engine and are deposited in the form of oxides within the particles of soot on the upstream face of the particle filter.
During phases of regeneration of the particle filter the metallic oxide residues, usually referred to as ash, are retained on the upstream face of the particle filter. Accordingly, during prolonged use of the pollution removing device, the accumulated ash significantly reduces the properties of the particle filter and in particular its ability to be regenerated. For a pollution removing device installed on a diesel-engined vehicle, deterioration of the properties of the particle filters has been observed at mileages exceeding 50,000 km.
Existing vehicles require replacement of the entire pollution removing device, which is a lengthy and costly operation.
The object of the invention is to propose a pollution removing device which reduces maintenance and service costs and guarantees satisfactory operation of the particle filter integrated therein over a long period.
To this end, the invention consists in a device for removing pollution from the exhaust gases of an internal combustion engine, of the aforementioned type, characterized in that the exhaust box includes means providing access to the upstream face of the particle filter, which access means have a cross section sufficient to enable cleaning of the particle filter by removal of ash retained on the upstream face of the filter.
In particular embodiments of the invention, the pollution removing device has one or more of the following features:
it includes means providing access to the downstream face of the particle filter;
the exhaust box has an outer jacket delimiting an exhaust gas flow passage across which are disposed the catalytic purification unit and the particle filter, and said access means include an orifice in the outer jacket opening opposite the corresponding surface of the particle filter and a removable cap for blocking said access orifice;
the exhaust box has an outer jacket delimiting an exhaust gas flow passage across which are disposed the catalytic purification unit and the particle filter and said access means include a transverse interruption of the outer jacket extending all around its periphery, which interruption separates the outer jacket into two successive sections, and means for removably butt jointing two successive sections at said interruptions;
the removable connecting means include, at the facing ends of each section, peripheral flanges and a clip for axially clamping the two flanges together;
said peripheral flanges are formed by deforming the ends of the successive sections;
the removable connecting means include a clamping ring attached to the end of each section and bolts for clamping the two clamping rings;
the free cross section of the transverse interruption is more than 60% of the cross section of the corresponding face of the particle filter;
the free section of the transverse interruption is greater than the maximum section of the particle filter, to enable the latter to be removed;
the removable butt jointing means include a seal disposed between the two successive sections.